Temperature and humidity: 

The life cycle progression of fruit flies, like other insects, is dependent on the temperature at which they are kept. While room temperature is ideal for maintaining flies, they can tolerate colder temperatures. If necessary, they can be refrigerated (NOT FROZEN) for about a week without inflicting any harm to the flies at any stage of life. Refrigerating the flies will cause them to be very sluggish or immobile until temperatures warm up. As a result, temporary refrigeration can be used to separate/transfer flies elsewhere. As long as there is adequate air exchange, and the media is properly hydrated, humidity isn’t a crucial factor.

Medium:

The medium provided is a potato-based proprietary mixture containing superfood products (including beet root and spirulina) for supplemental nutrients, like carotenoids, which have been shown to extend the lives of fruit flies as well as gives your pets (who eat the flies) better nutrition. Media should remain hydrated at all times. It should be smooth (like thick mashed potatoes), but never runny or sticky. Otherwise, adult flies will become trapped in the media and suffocate. If media is too dry, cracks may appear. Media that is not properly hydrated will delay the production of flies. To rehydrate, simply add water (slowly and little by little) until media appears smooth.

Detailed Fruit Fly Culture Preparation:

Materials needed to create a fruit fly culture container:

• 24 – 32 oz clear containers with a poly fabric lids

• Dry fruit fly medium

• Water

• Excelsior (wood wool)

• Flies (D. melanogaster or D. hydei)

Instructions:

The following instructions are for 10 oz of fruit fly medium. Adjust proportions (scale up or down) according to your needs.

1. Place 7 oz of warm/hot water into a mixing container

2. Ideally, while stirring, slowly add 3 oz of powdered medium to the water.

3. Stir until there are no clumps and a smooth slurry is formed. (Medium should have the consistency of thick mashed potatoes. It should be thin enough to be able to be tapped down to the bottom of the container, yet thick enough not to move if container is inverted.)

4. Allow slurry to sit for 2 minutes before assessing consistency (to absorb water.

5. If consistency is “good” after this 2-minute period, cover container and allow slurry to cool to room temperature.

6. Once medium has reached room temperature, add 3 – 4 oz of medium to each 24 – 32 oz container.

7. Firmly tap each container until the medium is flattened down to the bottom.

8. To each container, “loosely” add enough excelsior (wood wool) to each culture container.

9. Add flies (20- 50 flies) to each blank culture (If you are not yet ready to add flies, empty/blank cultures can remain stored in the refrigerator for up to one week. If stored, use plastic/aluminum wrap over the top of the poly fabric lid to prevent loss of moisture.)

Troubleshooting cultures:

Mold – In most cases, mold growth may begin while larvae (maggots) are small, but as they grow larger and the media becomes more populated, the growth will stop and likely become undetectable. The larvae produce antimicrobial compounds as they feed which inhibits mold growth! Just like how maggots can be used medically to eat decaying tissue on a patient while leaving behind these antimicrobial compounds to prevent further decay and infection!

Change in media color – In most cases, the color of media will change over time as the nutrients become depleted by the larvae; however, in some cases, media color can change a couple of days after inoculating a new culture. This media contains red pigment from a natural (vegetable) source. Many naturally occurring pigments change colors due to several factors. For example, color change can occur from reduction/oxidation (Redox) reactions and changes in pH. Neither of these cases will affect the quality of the media for your flies.

Dry media – If the media has cracks in it, it is likely too dry. To fix this, simply add water or fruit juice in very small quantities until media appears smooth again.

Excessive moisture - Another indication that there is too much water is if the larvae begin to leave the media and crawl around the sides of the container.

Overpopulation – If there are too many adult flies in the culture, this will decrease the shelf life of the culture as there will be more eggs laid, and therefore, more larvae consuming the media. In some cases, the media will become spent and there will be thousands of tiny larvae in the container which will not have enough food to become adults.